This invention relates to a selectively light transmitting (here light is used in a comprehensive sense to cover ultraviolet and infrared rays as well as visible radiation) or electrically conductive multilayer sheet material. More specifically it relates to a selectively light transmitting or electrically conductive film and a preformed self-supporting flexible laminar structure made therefrom.
In recent years, research and development of a selectively light transmitting film represented by a heat reflecting film or solar radiation controlling film have been prosecuted energetically with the object of saving energy in air conditioning by applying to building windows and the like. In U.S. Pat. Nos. 4,166,876, 4,226,910 and 4,234,654, for instance, the selectively light transmitting film is disclosed.
Further, U.S. Pat. No. 3,718,535 points out that it is well known that resistance to shatter in a window, aircraft canopy, windshield or the like can be markedly enhanced by providing a safety glass-type construction, i.e., one wherein flexible plastic interlayer films are disposed between and laminated to rigid transparent dielectric plies of, e.g., glass or polymethyl methacrylate. Furthermore, it is proposed to obtain a safety glass-type defroster by making the safety glass-type construction electrically powerable with a film bearing on at least one surface a thin electrically conductive metal coating placed in the construction. In U.S. Pat. Nos. 3,718,535, 3,816,201, 3,962,488, and 4,017,661, the safety glass-type defroster is disclosed. Also in UK Pat. No. 1,586,889 and Japanese patent application Laid-Open 32352/81, it is proposed to make a safety glass-type construction by use of a heat reflective film.
In case where a functional safety glass-type construction is formed by placing a functional film, which is made to have a function to reflect heat, control solar radiation, or conduct electricity, in a safety glass-type construction, it is necessary to see that the presence of such functional film will not degrade the resistance to shatter and further that the appearance will not be injured.
As a result of patient study to achieve the abovementioned objects, the inventors of the instant invention have come to find that, when the base film of said functional film is made thin in thickness, the presence of the functional film does not cause the degradation of the resistance to shatter of the safety glass-type construction and also that the fitability of a sag-formed doublet glass is improved. However, it has also come to be noted that, when the base film is made thin, the film develops wrinkles or creases in the safty glass-type construction, which deteriorate the see-through transparency, deforms the reflected image, and ruins the appearance, thus much detracting the commercial value of the construction. Therefore, the inventors have continued the study in an effort to obtain a functional film which will not ruin the appearance and have finally completed the instant invention.